1. Field of the Invention
The present invention relates to an ice making machine for making ice by means of a cooling function of an evaporator in a refrigeration circuit and accomplishing de-icing through a rise in temperature of the evaporator.
2. Description of the Prior Art
As one example of a conventional kind of ice making machine, the machine disclosed in Japanese Patent Laid-Open No. 2000-213841 is known. As shown in FIG. 11, in this machine a compressor 1, a condenser 2, a receiver 3, a dryer 4, an expansion valve 5, an evaporator 6, and an accumulator 7 (i.e., a liquid separator), are connected in a circulatory manner by refrigerant piping. Of these components the compressor 1, the condenser 2, and the accumulator 7, are disposed in an external unit, and the remaining components are disposed in an internal unit. On the outlet side of the condenser 2 is disposed a condensing pressure regulating valve 8 (CPR) to allow the flow of hot gas from the compressor 1 to the receiver 3 through a bypass line 1A. Further, characteristically, a gas outlet 3A is provided at the receiver 3. This gas outlet 3A is connected to an inlet of the evaporator 6 by a gas line 9 that is provided with a valve 9A partway along the gas line 9.
The operation of this conventional example is as follows. At the time of ice making, as known in the art, ice is formed by a refrigerating action imparted to latent heat (i.e., an endothermic action). The refrigerating action is generated when liquid refrigerant is vaporized inside the evaporator 6.
In contrast, at the time of de-icing, when the valve 9A of the gas line 9 is opened, low-temperature refrigerant gas inside the receiver 3 is introduced into the evaporator 6. The evaporator 6 is heated to conduct de-icing by latent heat produced when this gas condenses (i.e., an exothermic action). At the same time, because the pressure on the high pressure side decreases, the CPR 8 operates so that hot gas from the compressor 1 is supplied to the receiver 3 through the bypass line 1A to promote vaporization of the liquid refrigerant inside the receiver 3, whereby more refrigerant gas is introduced into the evaporator 6 to continue the de-icing.
The fundamental function of the CPR 8 in the refrigeration cycle described above is as follows. For example, in a case such as in wintertime when the outdoor air temperature is low and the cooling capacity of the condenser 2 has become excessively high, when the pressure on the high pressure side of the compressor 1 drops to a predetermined value the CPR 8 is activated to allow hot gas from the compressor 1 to flow to the side of the receiver 3, to thereby accumulate liquid refrigerant in the condenser 2 and reduce the cooling capacity. Naturally, in a case such as in summertime when the outdoor air temperature is high, the CPR 8 exerts the maximum cooling capacity by, conversely, closing the channel on the side of the bypass line 1A to allow high-temperature, high-pressure refrigerant from the compressor 1 to flow into the condenser 2.
However, when this refrigeration cycle is assessed with respect to its de-icing function, the following problem emerges. That is, when the outside air temperature is not remarkably high, there is no problem with the de-icing performance because hot gas from the compressor 1 is supplied to the receiver 3 through the bypass line 1A by the above-described action of the CPR 8. However, when the outside air temperature is high, the hot gas from the compressor 1 is fed to the receiver 3 after being cooled in the condenser 2, thus causing a decrease in the de-icing performance.